As a new construction technology, self drilling anchor system has been widely applied in hydroelectric station. It overcomes technical difficulties in loose rock conditions, realizes the primary stabilization by combining jetting cement and drainage hole method.
Self drilling anchor bolt is the main operating unit in self drilling anchor system. It is hollow and has full thread on surface. Coupling is adopted to lengthen it and one-off drill bit is installed on the front end.
Because of special structures, self drilling anchor bolt has following advantages:
1. High efficiency: self drilling anchor bolt combines drilling, grouting and anchoring together, which can be done at the same time, time-saving and high-efficient. Compared with common anchor bolt, it decreases the processes of pulling out of hole, installing anchor bar and inserting grouting pipes, which is quick and simple.
2. High adaptability: It is suitable for stratum which is difficult to drill hole, such as loose and broken surrounding rocks. After drilling holes, anchor bar stays in the hole, which avoids collapse, saves time and reduces construction difficulties. With whole thread on surface, it can be cut at any position. So it is suitable for different construction conditions.
3. High anchoring force and good anchoring effect: The thread of self drilling anchor bolt is generally R-thread or T-thread. They connect with coupling tightly and have good bonding effect with grouting slurry. When grouting, slurry is from the bottom to orifice, full and dense. Grouting quality is good.
Besides, self drilling anchor bolt in high slope of hydroelectric station has other features, such as big tensile pulling force of single anchor bolt, great depth, control or reduction occurrence of rock burst, enhance ability of anti-seismic and control deformation effectively.
On September 8, CRG announced that it had won a railway construction bid for section I, II, and III of the Boten-Vientiane Railway Project (also known as the China-Laos Railway), together with the Laos-China Railway Company Limited in Laos.
April 15th, 11:30am (local time) Ecuadorian Sopladora Hydropower Station, the first EPC project undertaken by CGGC in South America, had its power generation target accomplished – its first generator unit was connected to the electricity grid.
Paute-Sopladora Hydropower Station, located at the east border of Azuay Province and Canar Province, is a vital component of the hydropower generation project of Paute River basin. This station is equipped with three mixed-flow generators whose water head for electric generation is as long as 375.6m, with the total rated power at 487.8MW. Upon completion, this station will convey generated energy accounting for 13.9% of the domestic power demand to the national power grid, serving 1.3 million households. In consequence, it economizes annually on fuel consumption and energy import expenses in the amount of 200 million US dollars and, meanwhile, reduces emission of CO2 by nearly 1.7 million tons.
With the increase of Chinese enterprises to invest and participate in hydropower project, Metis® self drilling anchor system will be more widely applied in the field. It combines with drilling, grouting and anchoring, and the length can be cut according to the project. After grouting, slurry is filled with self drilling anchors and the surrounding rock. It can improve the anchoring effect, providing effective support for the project.
The grout mix is an essential part of the self-drilling anchor system providing the interface between the bar and the ground formation. Placement of the grout mix can either be subsequent to the drilling which is referred to as Post Grouting or combined with the drilling which is called Simultaneous Drilling and Grouting. Depending on the method to be used, the appropriate grouting equipment needs to be planned and set up prior to installation.
The basic grouting equipment consist of:
A mixing unit in which all ingredients are brought together always in the same sequence. First the water, then cement and finally the defined admixtures ( eg. Filler such as flyash or ultra fine sand, chemical additives such as plasticers and/ or non shrink additives). The mixing unit shall be capable of producing a grout of uniform consistency with the workability and strength characteristics required by the design.
A pump unit with sufficient pressure capacity to transport the homogeneously mixed grout paste through the grout hose and the hollow system of the MAI self drilling anchor bar, exiting at the drill bit through the flush holes and filling the annulus of the borehole until it exits at the borehole mouth.
Suitable grouting equipment available and recommended are:
a)Separate mixing and pumping unit such as the Uni-grout grouting platforms
b) A single pass mixing and pumping unit like the MAI grout pump M400 NT